Portable and adjustable contra-angle dental instrument



May 5, 1970 MASANO KIDOKORO ETAL 3,509,629

PORTABLE AND ADJUSTABLE CONTRA-ANGLE DENTAL INSTRUMENT Filed Sept. 27, 196'? Y 2 Sheets-Sheet 1 y 1970 MASANO KIDOKORO ETAL 3,509,629

PORTABLE AND ADJUSTABLE CONTRA-ANGLE DENTAL INSTRUMENT Filed Sept. 27. 196'? I 2 Sheets-Sheet 2 United States Patent Japan Filed Sept. 27, 1967, Ser. No. 671,000 Claims priority, application Japan, Oct. 1, 1966, 41/91,834, 41/91,835, ll/91,836, 41/91,,837, 41/91,838, 41/91,839

Int. Cl. A61c 1/10 U.S. C]. 32-27 7 Claims ABSTRACT OF THE DISCLOSURE A contra-angle member of the conventional structure of a dental instrument is secured to a portable, pencilshaped handpiece includes a miniature DC motor, a speed governor for controlling the motor speed, and a storage battery for energizing the motor. The longitudinal axes of the motor and battery are aligned with the axis of the rotary shaft of the contra-angle member. The contra-angle member may be selectively adjusted to different orientations to allow the dentist to assume a comfortable posture irrespective of the location of the cutting. A pushbutton switch is provided on the handpiece and a recharging receptacle is disposed on the bottom of the handpiece for recharging the storage battery.

This invention relates to a portable self-contained dential instrument by which a dentist cuts cavities in decayed teeth or effects machining and/or polishing of dentures.

Heretofore it has been common practice to drive such a dential instrument by transmitting power from an electric motor through an endless belt to the hand piece. Alternatively, compressed air from an air compressor could be fed to a rotary vane wheel disposed within the hand piece through a length of flexible hose to transmit the required power to the hand piece of the dental instrument. Consequently, the dental instrument is separated from its source of power resulting in a large and bulky apparatus which is often cumbersome to work with. Further, the use of an endless belt or a length of flexible hose as a power transmission mechanism causes not only a frictional power loss but also a smaller working region for the dentist. Therefore any dentist who is required to perform delicate treatments often finds himself having to assume awkward and unbalanced positions. In addition, any mechanical vibration of the belt or hose involved is transmitted to his hand.

Accordingly, a principal object of the invention is to provide a new and improved dental instrument permitting any dentist using it to be able to assume a comfortable posture while easily operating the instrument.

Another object of the invention is to provide a new and 3,509,629 Patented May 5, 1970 improved self-contained portable dental instrument which is simple and safe in operation.

A further object of the invention is to provide a new and improved self-contained portable dental instrument which has means for preventing it from being driven at a speed in excess of a predetermined magnitude even if loading on the instrument varies.

An additional object of the invention is to provide a new and improved self-contained portable dental instrument in which the contra-angle may be selectively fixed to its hand piece at predetermined orientations.

Briefly, the invention accomplishes the above cited objects by the provision of a portable dental instrument comprising a hand piece in the form of a pencil, a contraangle member mounted at one end of the hand piece including a rotary shaft and an interchangeable bar, a miniature DC electric motor disposed within the hand piece, and a source of electrical energy disposed within the hand piece to energize the motor.

Preferably, the source of electrical energy is a rechargeable storage battery or an accumulator and the hand piece is provided at one end with a receptacle for use in recharging the accumulator by the external charging device.

The hand piece may conveniently have a normally open pushbutton switch disposed on a reduced portion thereof. Only during manual depression of the pushbutton is the motor put in its energized state.

In order to prevent the motor from rotating at a speed above a predetermined magnitude, and speed governor mechanism may be provided for controlling the motor.

Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a digrammatic front elevational view of a dental instrument constructed in accordance with the invention;

FIGURE 2 is an enlarged longitudinal sectional view, partly in elevation of the instrument illustrated in FIG- URE 1;

FIGURE 3 is a sectional view taken along the line IIIIII of FIGURE 2;

FIGURE 4 is a fragme'ntal exploded perspective view of a contra-angle member and the adjacent end portion of a hand piece illustrated in FIGURES 1 and 2;

FIGURES 5 is a perspective view of a coupling illustrated in FIGURE 2;

FIGURE 6 is a schematic diagram of an electric circuit which may be used with the invention; and

FIGURE 7 is a schematic diagram of a charging circuit adapted to be used to charge a storage battery disposed within the present invention.

Referring now to the drawings and FIGURES 1 and 2 in particular, there is illustrated a dental instrument constructed in accordance with the invention. The instrument comprises a grip or a hand piece generally designated by the reference numeral 10 and including a main body 12 of any suitable plastic material in the form of a hollow cylinder. A tip member 14 of any suitable plastic material in the form of a truncated hollow core having an enlarged end portion is screw threaded at 16 into the adjacent end portion of the main body 12. A bottom cover 18 of any suitable plastic material screw threaded at 20 into the other end portion of the main body 12 to close the latter.

Disposed in the interior of the main body 12 and on the side near the tip member 14 is a miniature electric DC motor 22 including a rotary shaft 24 extending toward the tip member 14. A speed governor mechanism 26is directly coupled to the rotary shaft 24. The governor mechanism 26 serves to prevent the speed of rotation of the motor 22 from increasing above a predetermined magnitude. A closing cylindrical storage battery or accumulator 28 is disposed within the main grip body 12 on the side of the governor mechanism 26 opposite the motor 22 with a spacer 30 of any suitable plastic material interposed therebetween. In order to electrically connect the motor 22 to the battery 28, the spacer 30 is provided with an electric contact 32 adapted to electrically connect the positive pole of the battery 28 to the positive terminal of the motor 22 through a lead 34 when the battery is in place. The motor 22 is held in place within the main body 12 of the hand piece by a locking screw 36 threaded into the wall of the main body 12.

As best shown in FIGURE 2, the tip member 14 has carried at the reduced end a contra-angle member of well known construction designated by the reference numeral 38. The contra-angle member 38 has a retaining shaft 40 integral therewith and extending within the tip member 14 to be firmly and adjustably secured to the latter, and a thin rotary shaft 42 rotatably fitted into the retaining shaft 40 and supported by a suitable bearing 44 such as an oil impregnated hearing. The rotary shaft 42 is provided with a cross pin 46 projecting bilaterally thereof and aligned with the motor shaft 24. The contra-angle member 38 has an operating lever 48 well known in the art and mechanically connected to the retaining shaft 40. The op erating lever 48 is operative to engage and disengage the contra-angle member 38 with and from the tip member 14. Also the contra-angle member 38 has an interchangeable drill bit or burr 50 removably mounted at the exposed end.

In FIGURE 2 it is noted that the longitudinal axes of the motor 22 and the battery 28 are substantially aligned with the axis of the rotary shaft 42 and that the hand piece 10 containing the above-mentioned components is formed substantially into a pencil shape to be easily gripped by the fingers of a dentist.

As also shown in FIGURE 2, the cover 18 is provided on its external side with a cylindrical recess where a receptacle assembly, generally designated by the reference numeral 52, is attached for the purpose of charging the battery 28 by any suitable external source of direct current (not shown). The receptacle assembly 52 includes a contact pin 54 adapted to be electrically connected to a negative terminal of an external charging device (not shown), a cup-shaped contact sheet 55, a washer 56 of any suitable electrically insulating material for electrically insulating the pin 54 from the cups 55, and a U-shaped contact strip 58 adapted to connect the pin 54 to the negative pole of the battery 28'.

The hand piece 10 is provided with a normally open pushbutton switch, generally designated by the reference numeral 60, for energizing the motor.

As shown in FIGURE 3, the switch 60 comprises a movable contact strip 61 in the form of a segment fixed at one end on the internal wall surface of the enlarged end portion of the tip member 14 as by a rivet, a stationary.

contact strip 62 suitably fixed on the same wall surface with the free end portion of both contact strips opposed in slightly spaced relationship to each other. A short rod or a button 63 of any suitable plastic material loosely extends through the tip member 14 and is secured to the contact strip 61. The button 63 projects somewhat beyond the external wall of the tip member 14 and can be manually pushed to engage the movable contact strip 61 with the stationary contact strip 62 and thereby close the switch 60.

As shown in FIGURE 6, wherein like reference numerals designate like components corresponding to those illustrated in FIGURES 2' and 3', the switch 60 is connected in a series circuit including the battery 28, the motor 22 and the contacts controlled by the governor mechanism 26 which are connected across a capacitor 79. The capacitor 79 serves to protect the governor contacts from arcing and also to prevent wave interference. The switch 60 can be closed to complete the circuit with the motor 22 only when the button 63 is in its pushed position.

Referring now to FIGURE 4, the tip member 14'is provided on the reduced end face with a plurality of similarly shaped axial notches 64, 65, 66 and 67 disposed at substantially equal angular intervals. The retaining angle shaft 40 is provided with a single protrusion 68 complemental in shape to the notches and adapted to selectively engage one of the notches 64, 65, 66 or 67. As shown in FIGURE 2, the retaining shaft'40 has a ring 70 rigidly secured on the end opposite the protrusion 68. Disposed between the ring 70 and the inside of the reduced tip end is a compression spring 72 tending to normally bias the contra-angle member 38 toward the end of the tip member 14 thereby preventing the protrusion 68' from disengaging from the particular notch engaged by it.

In order to couple the motor shaft 24 to the rotary shaft 42, a cylindrical coupling 74 of any suitable plastic material is employed. The coupling 74 has the motor shaft 24 rigidly secured on one end portion and a central hole 76 axially drilled in the other end portion. A pair of diametrically split slots 78, greater in depth than the protrusion 68 on the retaining shaft 40 are provided in the coupling 74 as shown in FIG. 5. The rotary shaft 42 is inserted into the central hole 76 while the cross pin 46 is fitted into the slots 78 whereby the motor and rotary shafts 24 and 42, respectively, are substantially aligned with each other and in power transmission relationship.

In operation, a dentist can grip the dental instrument such that the main grip body 12 is placed on the root portions of his right thumb and index finger while the tip member 14 is gripped by the same fingers and the middle finger. Then he puts the contra-angle member 38 into a mouth of a patient such that the burr approaches a decayed tooth, after which the dentist pushes the switch button 63 by his thumb or index finger. This causes the switch to be closed thereby energizing the motor 22 within the main body 12 by the battery 28 resulting in rotation of the motor. The motor 22 transmits its torque through the coupling 74 and the rotary shaft 42 to retationally drive the burr 50.

Under these circumstances, it will be appreciated that loading on the burr 50 depends upon the particular decayed tooth. If loading on the burr 50 decreases causing the motor 22 to increase its speed of rotation above a predetermined magnitude, then the governor mechanism 26 operates to disconnect the motor 22 from the battery 28 to slow down the motor. If the motor speeds down to its lower limit, the governor mechanism 26 is ineffective for disconnecting the motor 22 from the battery 28. Thus the motor 22 is again energized by the battery 28.

The process as above described is continuously repeated unless the switch button 63 is released. Upon releasing the switch button 63, the rotation of motor 22 terminates.

If a decayed tooth on the upper jaw is desired to be cut, then the contra-angle member 38 is manually pulled up against the action of the spring 72 to disengage the protrusion 68 from the notch 64 previously engaged by the protrusion. Then the contraangle member 38 is manually rotated with respect to the hand piece 10 about the axis of rotation of the same until the protrusion 68 engages the notch 66 diametric to the notch 64 with the result that the contra-angle member 38 assumes the position illustrated in dot-and-dash lines in FIGURE 1 in which the contra-angle member 38 is tilted in a reverse direction from its previous direction. It is to be noted that the switch button 63 remains in the same orientation as in the previous case. This permits the switch button 63 to be similarly operated by the right thumb or index finger of the dentist.

Also (dependent upon which surface of a decayed tooth is to be cut, the protrusion 68 on the retaining shaft 40 may conveniently engage either of the remaining notches 65 or 67 to orient the contra-angle member 38 in such a direction that a dentist can easily use the present instrument with no change in orientation of the switch button 63.

It is apparent that after the dental instrument has been repeatedly used, the energy stored in the storage battery 28 is exhausted. At that time, the battery 28 must be recharged. Under these circumstances, the receptacle 52 disposed on the bottom cover 18 can be electrically connected to a pair of output terminals of any suitable charging device such as that generally designated by the reference numeral 80 in FIGURE 7. The charging device 80 comprises a pair of input terminals 81 and 82 adapted to be connected to any suitable source of commercial alternating current, and a step-down transformer 84 having a primary winding connected across the input terminals 81 and 84 through a switch 86. The secondary winding of the transformer 84 is connected across a pair of AC input terminals of a rectifier bridge 88 comprising four semiconductor diodes. The bridge 88 has a pair of DC output terminals 89 and 90.

With the output terminals 89 and 90 connected to the contact pin and contact cup, 54 and 55 of the receptacle 52, respectively, the battery 28 can be fully charged by the charging device 80 which itself is energized by an external source of alternating current through the now closed switch 86. Then the receptacle 56 can be disengaged from the output terminals 89 and 90 of the device 80 whereupon it is ready for future use.

The invention has several advantages. For example, it eliminates the necessity of providing a large-sized dental electric motor or air compressor along with their associated components which has previously been required to drive a drill bit or burr. The dental instrument according to the present invention is small, inexpensive and simple in construction. Also, the elimination of an endless belt or an increase in the length of flexible hose perunits a working region Within which a dentist can perform a treating operation and allows the dentist to assume an easy posture suitable for cutting the particular tooth of a patient. This results in a great decrease in his fatigue as compared with the conventional apparatus using an endless belt or a length of flexible hose.

Since a storage battery is used as a source of electric power and the recharging receptacle is disposed on the hand piece itself, the battery can be fully charged in the nighttime and ready for use the following day. Furthermore, a dentist can carry the portable instrument of the present invention and make a call on a patient at his house. In addition, the battery can be recharged without being removed from the hand piece.

As previously described, the switch for controlling the operation of the motor is disposed on the enlarged end portion of the tip member 14 and the motor is energized only when the switch is manually put in a closed position. The switch can be opened and closed by the dentists fingers while the contra-angle member is held in a mouth of a patient. Therefore the present instrument can be conveniently operated as compared with the conventional apparatus which includes a foot switch adapted to be manually closed after the associated contra-angle member has been placed into a mouth of a patient. The manual release of the switch button of the present invention ensures the prevention of any danger that might occur in a mouth of a patient. Thus the present instrument can be operated with a high degree of safety.

The provision of the speed governor mechanism for preventing the motor from rotating at excessively high speeds perm-its the torque of the motor to be transmitted to the contra-angle member at substantially constant speed despite various loading conditions. Further, an amount of tooth material to be cut can be maintained substantially constant whereby any patient is prevented from suffering pain due to excessive cutting.

As previously described, the notches 64 to 67 inclusive on the tip member 14 cooperate with the protrusion 68 on the contra-angle member 38 to provide means for fixing the contra-angle member to the hand piece 10 in one of any predetermined orientations relative to the latter. Therefore, if a different decayed tooth is desired to be cut, it is only necessary to vary the orientation of the contra-angle member while the orientation of the switch button 63 remains unchanged. Accordingly, a dentist using the present instrument can push the switch button 63 under a stable pressure by his accustomed finger.

It will be seen that, if the contra-angle member is rotated relative to the hand piece to vary its orientation, the axis of the rotary shaft 42 may be somewhat offset from the axis of the motor shaft 24. In this event the invention permits the torque of the motor to be effectively transmitted to the rotary shaft without hindrance by means of the cross pin 46 on the shaft 42 engaging the slots 78 on the coupling 74.

While the invent-ion has been illustrated and described in conjunction with a preferred embodiment thereof it is to be understood that numerous changes and modifications may be resorted to without departing from the spirit and scope of the invention.

What we claim is:

1. A portable dental instrument comprising: a hand piece containing therein an electric DC motor and a source of electric energy to energize said DC motor; a contra-angle member mounted at one end of said hand piece and including a rotatably mounted shaft and a tool bit; and means for selectively adjusting the angular position of said contra-angle member with respect to said hand piece including a projecting member on said contra-angle member and a plurality of notches each sized to receive said projecting member on said one end of said hand piece.

2. A portable dental instrument as claimed in claim 1, wherein said source is a storage battery, and said hand piece is provided at its other end with a recharging receptacle for use in charging said storage battery by an external source of direct current.

3. A portable dental instrument as claimed in claim 1, comprising a normally open pushbutton switch disposed on said hand piece, said motor being energized only when said switch is manually put in its pushed state.

4. A portable dental instrument as claimed in claim 1, comprising a speed governor mechanism integral with said motor to maintain the rotational speed of said motor below a predetermined speed.

5. A portable dental instrument as claimed in claim 1, wherein said rotatably mounted shaft has a cross pin projecting bilaterally thereof; a coupling having an axial central hole therein into which said rotary shaft is positioned and a pair of slots receiving said cross pin; and means connecting said DC motor to the otherend of said coupling.

6. A portable device comprising: a hand piece housing a driving member therein; a head piece having a driven member driven by said driving member; coupling means engageably and disengageably mounting said head piece in a given axial position on an end of said hand piece for axial displacement manually away from said hand piece and manul rotation through a predetermined angular distance relative to said hand piece including means for automatically returning said head piece to said given axial position after said head piece has been manually disengaged and rotated through said predetermined angular distance, and additional coupling means for engageably and disengageably coupling said driven member to said driving member.

7. A device according to claim 6, including motor means disposed within said hand piece for driving said driving member; and switch means mounted on said hand piece for selectively energizing said motor means when said motor means is connected to a source of power.

References Cited UNITED STATES PATENTS 8 3,011,287 12/1961 Goldfarb 4639 3,109,238 11/1963 Marks 32-27 3,183,538 5/1965 Hubner 1522 3,210,847 10/ 1965 Prufer 32-27 FOREIGN PATENTS 549,080 4/1932 Germany.

WARREN E. RAY. Primary Examiner U.S. Cl. X.R. 31050, 68, 71, 75 

